Pneumatic tool



F. H. THOMAS PNEUMATIC TOOL June i8, 1929.

Filed oct. 5. 1927 'INI/ENTOR.

Patented June 1.8, 1929.

UNTED STATES PATENT OFFECE.

FLOYD H. THOMAS, OF MILAN, PENNSYLVANIA, ASSIGNOR TO INGERSOLL-RAND OOM-PANY, 0F JERSEY CITY, NEW JERSEY, A CORPORATION OF NEIN JERSEY.

PNEUMATIC TOOL.

,Application filed October 5, 1927. Serial'No. 224,145`

rllhis invention relates to pneumatic tools, but more particularly to anexhaust valve for pneumatic tools of the hammer type.

The objects of the invention are to relieve the compression from theends of the cylinder, to effect such relief from one end of the cylinderin synclironism with the admission of pressure fluid to the opposite endof the cylinder, and to control the flow of exhaust fluid from the endsof the cylinder.

Other objects will appear hereinafter, and to all of these ends theinvention consists of the combination ofelements and arrangement ofparts having the general modeof operation D substantially as hereinafterdescribed and claimed and illustrated in the ing drawings, in whichFigure l is an elevation in section of a pneumatic tool constructed inaccordance with the practice of the invention and showing thedistributing and relief valves in the respective position which theywill assume during the admission of pressure Huid to the rearward end ofthe cylinder, and

Figure 2 is a view similar to Figure 1 showing the valves in their otherextreme positions.

Referring more particularly to the draw ings, A designates a cylinder ofa pneumatic tool and B a piston reciprocable in the cylinder fordelivering' blows of impact on a working implement, only the shank C ofwhich is shown projecting into the front end 'of the cylinder A.

On the back end of the cylinder A is a valve block D which forms aclosure for the rearward end of the cylinder and has a valve chamber Ein the form of a cylindrical bore opening from the rearward end of thevalve block D in this instance supports a plate F having a reari 1ardsurface Gr` which serves as a seat for an oscillatory plate typedistributing valve H and also forms a closure for the rearward end ofthe valve chamber E.

The distributing valve H may be of a well known type adapted to controlinlet passages J and K leading to the rearward and front ends of thecylinder respectively. The valve H is preferably pivoted on a pin Lsuitably anchored in a back head O to project into an aperture P in thevalve H for holding said valve against lateral movement with respect toa valve chamber Q. wherein said valve is disposed. The valve chamber Qin this instance is formed within the back head O provided with apassage S through which pressure fluid from a suitable source of supplymay pass to the valve chamber Q for distribution by the valve H.

Disposed within the valve chamber E is a relief valve T of the spooltype having a rearward head U and a forward head V connected to therearward head by a stem lV.

The valve T in this instance is adapted to be,

actuated by pressure fluid under full line pressure, and to this end akicker passage X formed in the plate F affords communication between theinlet passage K and the upper end of the valve chamber E for admittingpressure fluid against the head U to vactuate the valve T forwardly.

In order to actuate the valve T in a rearwardly direction simultaneouslywith the admission of pressure'fluid into the rearward end of thecylinder A, a similar kicker pas sage Y is formed in the front end ofthe valve block D to establish communication between the rearward end ofthe cylinder and the front end of the valve chamber E.

Leading from the front end of the cylinder A to a point near therearward end of the valve chest E is an exhaust passage Z for conveyingexhaust fluid from the-front end of the cylinder. The rearward end ofthe exhaust passage Z is in this instance controlled by the head U ofthe valve 'I' which thus also controls communication between the exhaustpassage Z and an exhaust port b in the valve block D, preferably locatedabout midway between the ends of the valve chamber E.

The exhaust passage Z in this instance has a forward port c and a port dlocated rearwardly of the port c to establish communication between saidexhaust passage Z and the forward portion of the cylinder.

The port d is so located that it may be overrun by the piston B on itsforward stroke and this port thus serves as an exhaust port for thepressure fluid utilized for actuating the piston B in a forwardlydirection. The port c being located near the front end of the cylinderserves exclusively as a compression relief port, such compression beingexhausted through the exhaust passage Z and through the exhaust port bas will be more fully described hereinafter.

In order to convey the exhaust fluid from the front end of the cylinderand the com pression from the rearward end of the cylinder, an exhaustpassage e leads from a point rearwardly of the transverse median line ofthe cylinder to a point in the valve chamber E intermediate the freeexhaust port Z) and the front end of said valve chamber. The passage ecommunicates at its front end with the cylinder through a port f, and aport g suitably located near the rearward end of the cylinder affordscommunication at this point between the cylinder and the passage e.

Communication between the passage e and the valve chamber E is in thisinstance controlled by the head V of the valve T which overruns thepassage e at this point to establish communication between said passagee and the exhaust port b.

In the operation of the device, with the left hand end of the valve Hraised as illustrated in Figure l, pressure fluid will flow through `theinlet passage J into the rearward end of the cylinder to actuate thepiston B in a forwardly direction against the working implement C. Uponthe admission of pressure fluid into the rearward end of the cylinder aportion thereof will pass through the kicker passage Y against the headV of the valve T and move said valve T rearwardly against the plate F toopen communication between the exhaust passage Z and the exhaust port Inthis way is established a direct path for the escape of compression ofthat portion of the cylinder forwardly of the piston B. Throughout thegreater portion of the forward stroke of the piston B compression mayflow from the cylinder through both ports CZ and c. However, after thepiston B covers the exhaust port cl, the port 0 alone will serve as anescape for the compression from the front end ofthe cylinder.

Immediately prior to the delivery of the blow of the piston B againstthe working implement C and port CZ will be uncovered by the piston andthe pressure fluid utilized for actuating the piston B forwardly willthen be exhausted through the port CZ, the exhaust passage Z into thevalve chamber E between the heads U and V of the valve and thencethrough the exhaust port Z) to the atmosphere.

Upon the exhaust of fluid from the rearward end of the cylinder' in themanner described, the pressure beneath the left hand end of the valve Hwill drop to such a value that the pressure fluid passing over said endwill create a suction of suliicient force there-` on to tip the valve Hto a position wherein the inlet passage eI will be closed and the frontinlet passage K will be uncovered. lith the valve in this positionpressure fluid will flow into the inlet passage K into the front end ofthe cylinder A for reversing the travel of the piston B.

At the instant of admission of pressure fluid to the front end of thecylinder, a portion of the pressure fluid flowing into the inlet passageK will pass through the kicker passage X against the rearward head U ofthe valve 'I" and actuate said valve to its extreme forwardmost positionwherein the head U of the valve T will cover the outlet opening of theexhaust passage Z and communication will be established between theexhaust passage c and the exhaust port As the piston B proceeds in arearwardly direction, the air in the rearward end of the cylinder A willbe expelled through the ports f and g into the exhaust passage e, thencethrough the valve chamber E and through the exhaust port Z) to theatmosphere. The compression will be thus expelled through the ports fand g until the port f is cov` ered by the piston B, thereafter the portg only will function for this purpose. At about the time the piston Boverruns the port f the port g will be covered by the piston B. Thepressure fluid utilized for actuating the piston B rearwardly will thenbe exhausted through the exhaust passage e and associated passagesleading to the atmosphere and the compression trapped in the rearwardend of the cylinder A will serve to 'cushion the piston B to preventimpact against the valve block D.

I claim:

In a pneumatic tool, the combination of a cylinder and a piston, a backhead having a distributing valve chamber, a distributing valve in thedistributing valve chamber, a valve block forming a closure for thecylinder and having a relief valve chamber, an exhaustl port in thevalve block affording communication between the relief valve chamber andthe atmosphere, a plate interposed between the back head and the valveblock to form a closure for the relief valve chamber and to act as aseat for the distributing valve, inlet passages leading` from thedistributing valve chamber to the cylinder and controlled by thedistributing valve, kicker passages in the valve block and the plate forconveying pressure fluid into the ends of the relief valve chamber toactuate the relief valve simulta neously with the admission of pressurefluid to the ends of the cylinder, and exhaust passages leading from theends of the cylinder to the relief valve chamber for conveying exhaustfluid and compression from the cylinder to the relief valve chamber,said exhaust passages being controlled by the relief' valve. y

In testimony whereof I have signed this specification.

FLOYD I-I. THOMAS.

